1. Field of the Invention
The present invention relates to a novel polymeric compound which can be used as a base component for a positive resist composition, a positive resist composition containing this polymeric compound, and a method of forming a resist pattern using this positive resist composition.
Priority is claimed on Japanese Patent Application No. 2009-033273, filed Feb. 16, 2009, the content of which is incorporated herein by reference.
2. Description of Related Art
In lithography techniques, for example, a resist film composed of a resist material is formed on a substrate, and this resist film is subjected to selective exposure of radial rays such as light or electron beam through a mask having a predetermined pattern, followed by development, thereby forming a resist pattern having a predetermined shape on the resist film.
A resist material in which the exposed portions become soluble in a developing solution is called a positive-type, and a resist material in which the exposed portions become insoluble in a developing solution is called a negative-type.
In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have lead to rapid progress in the field of pattern miniaturization.
Typically, these miniaturization techniques involve shortening the wavelength of the exposure light source. Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are starting to be introduced in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a wavelength shorter than these excimer lasers, such as F2 excimer lasers, electron beam, extreme ultraviolet radiation (EUV), and X-ray.
Resist materials for use with these types of exposure light sources require lithography properties such as a high resolution capable of reproducing patterns of minute dimensions, and a high level of sensitivity to these types of exposure light sources.
As a resist material that satisfies these conditions, a chemically amplified composition is used, which includes a base material component that exhibits changed solubility in an alkali developing solution under action of acid and an acid generator that generates acid upon exposure.
For example, a chemically amplified positive resist composition typically contains a resin component (base resin) that exhibits increased solubility in an alkali developing solution under the action of acid, and an acid generator. If the resist film formed using the resist composition is selectively exposed during formation of a resist pattern, then within the exposed portions, acid is generated from the acid generator, and the action of this acid causes an increase in the solubility of the resin component in an alkali developing solution, making the exposed portions soluble in the alkali developing solution.
Currently, resins that contain structural units derived from (meth)acrylate esters within the main chain (acrylic resins) are widely used as base resins for resists that use ArF excimer laser lithography, as they exhibit excellent transparency in the vicinity of 193 nm (for example, see Patent Documents 1 and 2).
Here, the term “(meth)acrylic acid” is a generic term that includes either or both of acrylic acid having a hydrogen atom bonded to the α-position and methacrylic acid having a methyl group bonded to the α-position. The term “(meth)acrylate ester” is a generic term that includes either or both of the acrylate ester having a hydrogen atom bonded to the α-position and the methacrylate ester having a methyl group bonded to the α-position. The term “(meth)acrylate” is a generic term that includes either or both of the acrylate having a hydrogen atom bonded to the α-position and the methacrylate having a methyl group bonded to the α-position.
Further, in order to improve various lithography properties, a resin having a plurality of structural units is currently used as the base resin for a chemically amplified resist. For example, in the case of a positive resist, a base resin containing a structural unit having an acid-dissociable, dissolution-inhibiting group that is dissociated by the action of acid generated from the acid generator, a structural unit having a polar group such as a hydroxyl group, and a structural unit having a lactone structure and the like is typically used. Among these structural units, a structural unit having a lactone structure is generally considered as being effective in improving the adhesion between the resist film and the substrate, and increasing the compatibility with an alkali developing solution, thereby contributing to improvement in various lithography properties.    [Patent Document 1] Japanese Unexamined Patent Application, First Publication No. 2003-241385    [Patent Document 2] Japanese Unexamined Patent Application, First Publication No. 2006-016379